Display and input devices provided with a display device (e.g., a liquid crystal display) and a touch panel, which is an input device, placed in front of the display device have been put to practical use, and have been used in the operation panels of portable devices (e.g., mobile phones) and electrical home appliances. Display and input devices using touch panels enable users to intuitively operate the instrument by pressing the display on the screen.
In such a display and input device using a touch panel, the touch panel is placed in front of the display device, and is therefore required to have high transparency so as to increase the visibility of the display of the display device.
Mobile phones and tablet computers equipped with touch panels have rapidly spread in recent years. Their displays are viewed from a close distance, and are thus required to have a very high image quality.
Various resin films are used as optical films in such displays, and the quality of the resin films can have a large impact on the image quality of the displays.
Factors adversely affecting the quality of the optical films include, for example, the uneven thickness of the film, deposits of additives in the resin composition, unmelted parts of the resin, scratches, crosslinked gels formed from the resin, etc. Techniques for solving each of these factors are proposed (for example, PTL 1 to PTL 11).
Meanwhile, highly transparent touch panels that can detect the height (strength) of pressing force are proposed.
As such a touch panel, for example, PTL 12 proposes a touch panel comprises a transparent piezoelectric layer containing a vinylidene fluoride/tetrafluoroethylene copolymer that has a low total haze value.
Further, PTL 13 discloses a polarized vinylidene fluoride/tetrafluoroethylene copolymer film that has substantially no anisotropy and has few scratches on the surface.